The court was told an incredibly harrowing tale of a woman struggling to cope with her 18-year-old son, who she believed suffered from Asperger's syndrome, and his disturbing obsession with child pornography.

A distressed Earl informed her son he could be arrested, and he replied that he would rather kill himself than face jail.

So when he was arrested on December 18, 2013, she went to the Gold Coast University Hospital - where she had worked since 2010 - and obtained anaesthesia drugs.

Upon his release from the watch-house the next day, she administered the drugs to her son, and he died in their home.

Earl took the family dog to the vet to be put down, and then administered the drugs to herself.

But she woke up the next day, much to her distress, and was later arrested for murder.

The charge was downgraded to manslaughter because the Mental Health Court determined she had diminished responsibility due to mental health issues.

Justice Roslyn Atkinson said it was an unusual case and sympathised with Earl, who stood in the dock sobbing throughout her sentencing hearing.

"Essentially, you helped him to die out of your great love for him," Justice Atkinson said.

"The problem is, that's a crime.

"There are not many cases where a killing is committed out of love ..."

Earl told the court she only wanted to say one thing: "I loved him very much. It was a privilege to be his mum".

She will be released on parole in three months.

For support and information about suicide prevention, call Lifeline 131 114; Suicide Call Back Service 1300 659 467.